A-  f,  t  '  <^3/p-c  >  if 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ENTOMOLOGY— BULLETIN  No.  85,  Part  YL 

L.  O.  HOWARD.  EntomoloBsl  and  Chief  of  Bureau. 


PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 


CONTRIBUTIONS  TO  A  KNOWLEDGE  OF 
THE  CORN  ROOT-APHIS. 


•  BY 


R.  A.  VICKERY, 

Agent  and  Expert. 


Issued  July  12,  1910. 


WASHINGTON: 

GOVERNMENT    PRINTING     OFFICE, 
1910. 


BUREAU  OF  ENTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  Chief  of  Bureau. 

C.  L.  Marlatt,  Assistant  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 
W.  F.  Tastet,  Chief  Cleric. 

F.  H.  Chittenden, i;i  charge  of  truck  crop  and  st(^7'ed  product  insect  investigations. 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

F.  M.  Webster,  in  charge  of  cereal  and  forage  insect  investigations. 

A.  L,  Quaintance,  in  charge  of  deciduous  fruit  i)iscct  investigations. 

E.  F.  Phillips,  in  charge  of  dec  culture. 

D,  M.  Rogers,  in  charge  of  preventing  spread  of  moths,  field  icork. 
RoLLA  P.  Currie,  in  charge  of  editorial  work. 

Mabel  Colcord,  lihrarian. 

Cereal  and  Forage  Insect  Investigations. 
F.  M.   AVebster,    in  charge. 

Geo.  I.  Reeves,  W.  J.  Phillips,  C.  N.  Ainslie,  E.  O.  G.  Kelly,  W.  W.  Yothers, 

J.     A.   HYSLOP,     V.     I..     WiLDERMUTH,    R.    A.     ViCKERY,     T.     H.     PaRKS,     HERBERT 

OsBORN,  Philip  Luginbill,  agents  and  experts. 
II 


CONTENTS. 


Page. 

Introduction 97 

Distribution 98 

History 98 

Experimental  work  in  the  South 100 

Uncultivated  food  plants 102 

Injury  to  corn 104 

Relation  of  ants  to  the  root-aphis 105 

Natural  checks 106 

Preventive  measures '. 106 

Crop  rotation 106 

Maintenance  of  soil  fertility 106 

Early  plowing,  followed  by  frequent  cultivations 106 

Repellents .-... 107 

Injury  to  cotton 108 

Injury  to  asters 109 

Other  cultivated  food  plants Ill 

Description  and  synonymy Ill 

The  Erigeron  root-aphis  ( Aphis  middletoni  Thos. ) 113 

Uncultivated  food  plants 114 

Cultivated  food  jjlants 115 

Attendant  ants 115 

Laboratory  and  field  experiments 116 

III 


ILLUSTRATIONS. 


PLATES. 

Page. 
Plate  V.  Fig.  1. — Damage  to  a  field  of  corn  in  Indiana,  in  1906,  by  the  corn 
root-aphis  {Aphis  maidi-radicis).     Fig.  2. — Same  field  a  year  later, 
showing  the  effect  of  applying  barnyard  manure 104 

TEXT   FIGURES. 

Fig.  54.  The    corn   root-aphis    {Aphis    maidi-radicis):     AVingless,    viviparous 

female 99 

55.  The  corn  root-aphis:  Winged,  viviparous  female 100 

56.  The  corn  root-aphis:  Oviparous  female 104 

57.  The  corn  root-aphis:  Wingless  male 104 

58.  The  corn  root-aphis:  Winged  male 112 

59.  Map  showing  distribution  of  Aphis  maidi-radicis  and  Aphis  middletoni 

in  the  United  States 114 

IV 


IT.  S.  D.  A.,  B.  E.  Bui.  85,  Part  VI.  C.  F.  I.  I.,  July  12,  1910. 

PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 


CONTRIBUTIONS    TO    A    KNOWLEDGE    OF    THE    CORN 

ROOT-APHIS. 

(Aphis  tnaidi-radicis  Forbes.) 

By  R.  A.  ViCKERY, 
Agent  and  Expert. 

INTRODUCTION. 

The  corn  root-aphis  (Aphis  mmdi-radicis  Forbes)  is  one  of  the 
many  insects  infesting  the  corn  phint  in  this  country.  It  has  cer- 
tainly been  known  as  an  enemy  of  corn  for  nearl}^  a  century,  and  per- 
haps much  longer.  Besides  corn  it  attacks  sorghum  and  broom  corn, 
but  does  little  damage  to  these  plants.  Within  the  last  three  years  it 
has  attracted  considerable  attention  as  an  enemy  of  cotton  in  the  Car- 
olinas,  where  it  feeds  on  the  roots  of  young  cotton  and  is  called  the 
"  root  louse  "  or  "  blue  bug."  Among  its  other  recently  ascertained 
food  plants  are  pumpkin,  squash,  straAvberries,  cultivated  asters,  and 
perhaps  dahlia  and  French  artichoke. 

Ever  since  this  insect  was  first  noted  by  Walsh  in  1862  it  has  re- 
ceived considerable  attention  from  economic  entomologists.  Its  life 
history  and  habits  in  Illinois  have  been  very  thoroughly  studied  by 
Dr.  S.  A.  Forbes,  state  entomologist,  and  his  assistants;  and  during 
the  past  three  years  it  has  been  studied,  under  the  direction  of  Prof. 
F.  M.  Webster,  by  the  assistants  in  Cereal  and  Forage  Insect  Investi- 
gations, Bureau  of  Entomology.  These  studies  have  been  made  over 
a  large  extent  of  country,  as  follows :  In  the  Northwestern  States  dur- 
ing the  season  of  1908  by  Mr.  E.  O.  G.  Kelly ;  in  Indiana  by  Mr.  W. 
J.  Phillips ;  in  South  Carolina  during  the  seasons  of  1908  and  190i)  by 
Mr.  G.  G.  Ainslie ; «  in  Florida  and  eastern  North  Carolina,  as  a  cot- 
ton insect,  by  Mr.  H.  F.  Wilson  under  the  direction  of  Mr.  W.  D. 
Hunter,  during  the  season  of  1909;  and  in  the  Piedmont  section  of 
North  Carolina  by  the  writer,  also  during  the  season  of  1909. 

<^  These  investigations  were  carried  on  by  Mr.  Ainslie  as  a  part  of  cooperative 
work  by  the  Bureau  of  Entomology  and  the  South  Carolina  experiment  station 
of  the  Clemson  Agricultural  College,  and  the  results  of  his  work  were  published 
by  Prof.  A.  F.  Conradi  in  the  twenty-second  annual  report  of  that  institution, 
for  the  year  ending  June  30,  1909,  pages  51  to  65. 

97 


98  PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 

An  apliis  frequently  infesting-  the  roots  of  EAgeron  canadensis  has 
generally  been  considered  as  belonging  to  this  species.  It  is  inchided 
in  the  latter  part  of  this  paper  for  this  reason,  but,  as  explained 
farther  on,  it  now  seems  to  be  distinct  from  the  corn  root-aphis,  and 
is  therefore  discussed  under  the  name  Aphis  middletoni  Thomas, 
with  the  description  of  which  it  seems  best  to  agree. 

The  illustrations  of  the  oviparous  female  and  wingless  male  of  the 
corn  root-aphis  (figs.  5G  and  57)  are  kindly  loaned  for  use  in  this 
paper  by  Dr.  S.  A.  Forbes,  state  entomologist  of  Illinois. 

DISTRIBUTION. 

According  to  the  letters  of  inquiry  in  the  files  of  the  Bureau  of 
Entomology  the  corn  root-aphis  has  been  seriously  injurious  to  corn 
in  the  following  States  (fig.  59)  :  New  Jersey,  eastern  Pennsylvania, 
Maryland,  Virginia,  West  Virginia,  North  Carolina,  South  Caro- 
lina, Ohio,  Indiana,  Illinois,  and  Oklahoma.  Besides  these  States 
it  has  been  reported  in  literature  as  injuring  corn  in  New  York,  Min- 
nesota, Iowa,  Missouri,  Nebraska,  Kentucky,  Mississippi,  Louisiana, 
and  Colorado.  In  addition  to  the  States  mentioned  above  the  root- 
aphis  was  collected  from  the  roots  of  corn  at  Sioux  Falls,  Huron,  and 
Aberdeen,  S.  Dak.,  by  Mr.  Kelly  of  the  Bureau  of  Entomology,  and 
what  is  supposed  to  have  been  this  species  was  collected  from  corn 
roots  at  Sterling,  Kans.,  by  Mr.  C.  N.  Ainslie,  also  of  this  Bureau. 
Injuries  to  cotton  have  occurred  in  the  coastal  plain  of  the  Carolinas. 
An  aphis  supposed  to  be  of  this  species  has  been  reported  to  the 
Bureau  as  injurious  to  cultivated  asters  from  the  following  States: 
Massachusetts,  Rhode  Island,  Connecticut,  New  York,  New  Jersey, 
Delaware,  Maryland,  Ohio,  and  Illinois.  The  species  is  apparently 
distributed  in  the  United  States  throughout  almost  the  entire  region 
east  of  the  Rocky  Mountains  wherever  corn  is  grown. 

It  has  been  reported  from  Maine  in  a  letter  to  the  Bureau,  but  on 
w^hat  food  plant  it  was  taken  is  not  known.  Although  Mr.  Kelly 
searched  for  it  in  North  Dakota,  Montana,  and  Wyoming  he  did  not 
find  it  in  those  States.  It  has  not,  up  to  the  present  time,  been  re- 
ported from  New  Hampshire,  Vermont,  Michigan,  Wisconsin,  Texas, 
Arkansas,  or  southern  Florida.  It  is  probably  present  in  Mexico, 
although  we  have  found  no  reference  to  it  in  any  of  the  foreign 
literature. 

HISTORY. 

Although  the  corn  root-aphis  (figs.  54—58)  was  not  described  and 
named  imtil  1891,  it  has  apparently  been  known  to  the  corn  growers 
of  this  country  for  nearly  a  century  and  possibly  much  longer. 
James  Worth,  in  an  article  entitled  "  Observations  on  Insects  "  read 
before  the  Agricultural  Society  of  Bucks  County,  Pa.,  July  29,  1822, 


CONTRIBUTIONS   ON    THE    CORN    ROOT-APHIS. 


99 


and  published,  in  the  American  Farmer ,«  mentioned  ''  a  species  of 
louse  or  aphis,  that  infests  grounds  and  feeds  upon  the  roots  of 
wheat,  corn,  J^oung  trees,  etc.,  and  do  immense  damage.''  And  Thos. 
W.  Emorv,^  in  Avriting  of  sedge  in  Avheat,  said : 

I  believe  that  this  insect  is  the  same  as  that  laiowii  by  the  name  of  root 
louse  in  corn,  so  frequently  found  in  that  plant,  growing  after  clover,  when 
the  land  is  early  flushed,  and  which  occasions  so  stinted  and  diseased  a 
growth  that  it  rarely  recovers  till  late  in  the  summer,  and  not  then  if  the 
season  is  dry.'^ 

Mr.  Emory  gave  his  address  as  Poplar  Grove,  without  mentioning 
the  State.  But  although  the  State  was  not  mentioned,  his  writings 
give  the  impression  that  he  was  talking  about  conditions  in  Maryland. 
From  these  two  notices  it  appears 
that  the  corn  root-aphis  was 
familiar  to  the  people  of  Pennsyl- 
vania and  Maryland  as  early  as 
18-22,  because  there  is  no  other 
aphis  on  the  roots  of  corn  connnon 
enough  to  have  been  so  generally 
known. 

In  Illinois  the  corn  root -a  phis 
was  first  studied  in  1862  by  B.  D. 
Walsh  near  Rock  Island,  where  it 
had  attacked  a  small  field  of  corn 
and  destroyed  about  half  of  it. 
Walsh  collected  specimens  from 
which  he  reared  winged  females 
(fig.  55),  and  from  the  similarit}^ 
of  these  to  the  corn  leaf-aphis  he 
decided  that  the}-  were  identical, 
and  in  an  essay  published  in  the 
Transactions  of  the  Illinois  Agricultural  Society  he  considered  the 
leaf-aphis  to  be  but  an  aerial  form  of  the  root-aphis.  This  view  was 
accepted  b}-  C3'rus  Thomas  and  later  writers  who  studied  the  species. 

Dr.  S.  A.  Forbes  began  his  study  of  this  insect  in  1883,  and,  as 
a  result  of  his  work  and  the  work  of  his  assistants,  came  to  the  con- 
clusion that  the  root-aphis  is  a  distinct  species.  So  he  described 
it  as  such  under  the  name  of  Aphis  maidi-radicis.^     His  studies  of 


Fig.  54. — The  corn  root-aphis  (Aphis 
maidi-radicis)  :  Wingless,  viviparous  fe- 
male, greatly  enlarged,  and  antenna, 
highly  magnified.      (From  Webster.) 


o  American  Farmer,  vol.  4,  p.  395,  March  7,  1823. 

&  Idem,  p.  71,  May  24,  1822. 

^  Webster,  F.  M. — Early  published  references  to  some  of  our  injurious  in- 
sects. Insect  Life,  U.  S.  Dept.  Agr.,  Washington,  D.  C,  vol.  2,  Nos.  7  and  8, 
p.  264,  1890. 

^  Seventeenth  Report  of  the  State  Entomologist  of  Illinois  for  1889  and  1890. 
Trans.  Dept.  Agr.  111.,  Spriugtield,  vol.  28,  pp.  64-70,  colored  plate  "  B,"  figs, 
l-l,  1891. 


100 


PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 


this  species  have  been  continued  till  now  its  life  history  and  habits 
as  a  corn  insect  in  Illinois  are  very  Avell  understood. 

Until  recently  it  has  not  been  so  thoroughly  studied  in  other  sec- 
tions of  the  country,  especially  in  the  Southern  States,  where  its  life 
history  and  habits  are  widely  different  from  what  they  are  in  Illinois. 
Some  of  the  results  of  these  more  recent  studies  Avhich  have  been  made 
by  the  Bureau  of  Entomology  are  therefore  presented  in  this  paper. 

EXPERIMENTAL   WORK   IN   THE   SOUTH. 

The  following  laboratory  experiments  were  carried  on  by  the 
writer  at  Salisbury,  N.  C,  to  determine  the  identity  of  the  aphides 


FiQ.  55. — The  corn  root-aphis  :    Winged,  viviparous  female,  greatly  enlarged,  and  antenna 
of  same,  highly  magnified.      (From  Webster. j 

found  on  the  roots  of  corn,  cotton,  and  various  weeds.  The  method 
used  was  to  remove  wingless  females  of  Aphis  maidi-radicis  from  the 
roots  of  the  various  food  plants  and  to  place  them  either  on  sprout- 
ing cotton  or  on  sprouting  corn  in  vials.  A  plug  of  wet  absorbent 
cotton  Avas  j^laced  in  the  bottom  of  the  vials.  The  roots  of  the  plants 
would  grow  down  into  this  and  would  keep  alive  and  furnish 
nourishment  for  the  aphides  for  about  a  week.  Cotton  plants  proved 
the  best  for  use  in  these  experiments  because  they  were  not  so  subject 
to  attack  by  fungi  as  were  corn  plants.  The  vials  were  kept  in  the 
dark.  The  aphides  usually  attack  tlie  leaves  of  the  cotton  in  pref- 
erence to  the  stem. 

Amhrosia    artemisiifol'ui     (bitter weed). — Experiment    a:    Apterous    vivipara 
were  removed  from  the  roots  of  this  plant,  September  18,  and  placed  on  sprout- 


COXTEIBUTIOXS    ON    THE    CORN    ROOT-APHIS.  101 

ing  corn ;  they  reproduced  aud  the  colony  was  kept  on  corn  till  November  30. 
Many  oviparous  females  and  2  winged  males  were  produced  by  this  colony. 
The  sexual  forms  appeared  October  15.  Experiment  &.'  Apterous  vivipara  were 
removed  from  the  roots  of  Ambrosia  and  placed  on  sprouting  cotton,  September 
24.  The  colony  continued  till  November  16,  producing  oviparous  females 
October  28. 

Chenopodium  album  (lamb's-quarters). — Two  vivipara  and  1  oviparous 
female  were  removed  from  this  plant  to  sprouting  cotton.  This  colony  did  well 
till  November  11,  when  the  2  oviparous  females  it  contained  were  removed  to 
alcohol. 

Diodia  teres  ( buttonweed ) . — Experiment  a:  Female  specimens  were  removed 
from  the  roots  of  this  plant  to  cotton.  July  29;  the  colony  did  well  till  August 
10,  when  it  was  killed  by  the  death  of  the  cotton  plant  from  disease.  Experi- 
ment &.'  Wingless  females  were  removed  to  corn,  July  28.  Young  were  pro- 
duced and  the  experiment  was  continued  till  August  30.  Experiment  c:  Seven 
wingless  females,  which  had  produced  young  on  corn  in  experiment  &.  were 
removed  to  cotton,  August  14.  They  produced  young  on  the  cotton  and  the 
colony  was  continued  till  November  22,  when  it  was  discontinued.  No  sexual 
forms  were  produced. 

Diodia  virginiana  (buttonweed). — Female  Individuals  were  removed  from 
the  roots  of  this  plant  to  sprouting  cotton,  September  25.  The  colony  did  well 
till  December  4,  when  it  was  discontinued.     No  sexual  forms  were  produced. 

Leptochloa  filiformis. — Experiment  a:  Females  were  removed  from  the  roots 
of  this  plant  to  sprouting  cotton,  September  13.  The  colony  was  continued  till 
December  8  without  producing  sexual  forms.  Experiment  &.'  Females  were  re- 
moved from  the  roots  of  Leptochloa  to  corn.  This  colony  continued  till  De- 
cember 4.  Oviparous  females  and  a  winged  male  were  produced,  and  eggs 
were  laid. 

Coj^. — Wingless  females  were  removed  fi'om  the  roots  of  corn  in  the  field  to 
sprouting  corn  in  a  vial,  June  16,  and  on  July  15  females  were  removed  from  the 
corn  in  this  vial  to  sprouting  cotton,  where  they  established  a  colony  which 
was  continued  till  August  16. 

These  experiments  show  that  if  the  apterous  females  of  Aphis 
maidi-radicis  are  transferred  to  the  roots  of  com  or  cotton  from  sev- 
eral of  their  wild  food  plants  or  if  they  are  transferred  from  corn  to 
cotton  they  will  produce  young  and  establish  colonies.  Thus  it  is 
possible  for  the  ants  to  transfer  the  aphides  from  a  dying  food  plant 
to  any  other  one  of  a  large  range  of  food  plants.  Fortunately  there 
are  man}^  cultivated  plants,  such  as  clover,  cowpeas,  wheat,  oats,  and 
rye,  used  in  various  systems  of  rotation,  which  this  insect  feeds  on  not 
at  all,  or  only  rarely  and  for  a  short  time. 

Mr.  G.  G.  Ainslie  experimented  in  a  diiferent  manner  near  Marion, 
S.  C,  to  determine  the  same  points.  Seeds  of  a  number  of  species  of 
cultivated  plants  were  planted  near  infested  corn  rows,  trusting  to 
ants  to  transfer  the  aphides  from  one  plant  to  another.  These  intro- 
duced plants  were  examined  June  5,  with  the  following  results: 
Muskmelon  plants  near  infested  cotton  were  well  provided  with 
aphides,  several  of  the  wingless  ones  being  found  with  young  about 
them.  Turnip  plants  near  infested  cotton  had  few  aphides  on 
40842— Bull.  85,  pt  6—10 2 


102  PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 

them.  Cowpeas  were  lightly  infested  with  all  stages,  except  mi- 
grants, although  not  located  near  heavily  infested  cotton.  On  beans 
near  infested  cotton  there  were  only  a  few  of  the  root-aphis.  Sweet 
corn  had  been  planted  along  a  row  of  cotton,  and  this  was  quite  gen- 
erally infested  Avith  the  '*  lice,"  plants  that  were  near  dead  cotton 
being  most  heavily  infested.  On  radish,  a  colony  was  found  on  one 
plant  growing  near  badly  infested  cotton.  Watermelon  plants 
which  had  just  unfolded  their  first  leaves  and  were  near  infested  cot- 
ton had  an  abundant  supply  of  the  root-aphis.  In  the  case  of  each  of 
the  cultivated  plants  mentioned  above,  ^Ir.  Ainslie  found  evidence 
that  the  "  lice  "  Avere  transferred  from  the  cotton  to  the  others  by  the 
ants.  The  ants  found  in  attendance  Avere  Lasiiis  niger  americanus^ 
Pheidole  dentata  comutata^  and  Pheidole  vinelandica. 

UNCULTIVATED    FOOD    PLANTS. 

Beside  the  cultiA^ated  plants  mentioned  above,  the  root-aphis  feeds 
on  various  uncultivated  species  which  are  enumerated  below. 

In  Illinois  it  has  been  rej^orted  by  Mr.  J.  J.  Davis  °  on  the  roots 
of  numerous  weeds  and  grasses,  as  follows :  Smart  weed  {Polygonum 
lafathifoliurri)  ^  knotweed  {Polygonum  j^  er sic  aria)  ^  crab  grass  {Digi- 
taria  sanguinalis) ,  purslane  {Portulaca  oleracea)^  dock  {Rumex 
crispus  and  R.  altissimus),  foxtail  or  pigeon  grass  {Setaria  glauca 
and  S.  viridis),  fleabane  {Erigeron  canadensis)  ^  mustard  {Brassica 
nigra) ^  sorrel  {Oxalis  stricta)^  plantain  {Plantago  major  and  P, 
rugelii)^  pigweed  {Amaranthus  hyhridus)^  and  ragweed  {Ambrosia 
tHfida), 

In  the  South  it  has  been  found  on  the  following  Avild  food  plants :  ^ 
At  Chattanooga,  Tenn.,  NoA^ember  25,  1909,  a  few  oviparous  females 
Avere  found  on  thorny  amaranth  {Amaranthus  spinosus).  ViAdp- 
arous  females  Avere  found  on  green  amaranth  {Amaranthus  retro- 
flexus)  in  a  cornfield  at  Salisbury,  N.  C,  October  12,  1909,  in  small 
numbers.  It  was  found  rarely  on  Roman  AvormAvood  {Ambrosia 
artemisiifolia)  at  Nathalie,  Va.,  by  Mr.  J.  A.  Hyslop,  July  10,  1908. 
It  was  found  in  large  numbers  on  the  roots  of  Ambrosia  artemisiifolia 
in  cotton  fields  and  in  Avaste  ground  at  Marion,  S.  C,  May  27  to  June 
5,  1909,  and  at  Salisbury,  N.  C,  May  22  and  September  18,  1909.  On 
this  plant  they  usually  fed  in  fair-sized  colonies  along  the  main  tap- 
root>  sometimes  10  inches  deep  in  the  ground.  It  Avas  found  on  dog 
fennel  {Anthemis  cotula)  in  very  large  colonies  at  the  base  of  the 
large  roots,  near  the  crown,  at  Marion,  S.  C,  on  May  29,  1909;  on 
shepherd's  purse  {Capsella  bursapastoris)  in  small  numbers  at  Salis- 

«DaAis,  John  June — Biological  Studies  on  Three  Species  of  Aphididse.  Tech. 
Ser.  No.  12,  Part  VIII,  Bur.  Ent,  U.  S.  Dept.  Agr.,  February  20,  1909. 

*  Records  from  Marion,  S.  C,  are  by  Mr.  G.  G.  Ainslie;  those  from  other 
localities  are  by  the  writer,  unless  otherwise  stated. 


CONTRIBUTIONS   ON    THE    COEN   ROOT-APHIS.  103 

bury,  X.  C,  June  16,  1909;  on  lamb's-quarters  {Chenopodiiim  album) 
growing  near  a  field  of  popcorn  at  Nathalie,  Va.,  by  Mr.  Hyslop, 
July  10,  1908,  and  on  the  same  species  growing  beside  a  cornfield  at 
Salisbury,  N.  C.,  October  9-22,  1909 — in  large  numbers  at  both 
places;  on  poverty  weed  (Diodia  teres)  in  a  cornfield  at  Salisbury, 
N.  C,  July  28,  1909;  on  buttonweed  {Diodia  rirginiajia)  in  a  corn- 
field at  Salisbury,  N.  C.,  September  25,  1909;  on  foxtail  or  pigeon- 
grass  {Setaria  glauca)  at  Marion,  S.  C,  June  3,  1909;  in  small  num- 
bers on  cudweed  {Gnaflialium  imrpureum)  at  Salisbury,  N.  C.,  May 
22,  1909,  and  in  large  numbers  on  this  plant  at  Marion,  S.  C,  from 
May  2G  to  June  14.  1909.  It  was  numerous  on  sneezeweed  {Heleniuvi 
tenuifoliiim)  at  Rockmart,  Ga.,  November  23,  1909,  and  at  Marion, 
S.  C,  May  29  to  June  25,  1909 ;  this  plant,  growing  in  open  ground, 
and  in  cotton  and  corn  fields,  was  the  most  commonly  infested  weed, 
and  was  heavily  infested  by  the  aphis  in  all  stages.  On  pineweed 
{Hypericum  gentianoides)  it  was  found  in  small  numbers  at  Marion, 
S.  C,  May  26,  1909.  It  was  abundant  on  dwarf  dandelion  (Krigia. 
virginica)  at  Marion.  S.  C,  May  26,  1909;  large  colonies  were  found 
near  the  crown  of  the  plant,  but  individuals  were  sometimes  deep 
down  on  the  fibrous  roots.  It  was  found  on  Leptochloa  filiformis  at 
Salisbury,  X.  C.,  September  13,  1909.  On  peppergrass  (Lepidium 
apetalum)  at  Ringgold,  Ga.,  November  24,  1909,  a  few  only  were 
found.  Lepidium  virginicum  was  a  favorite  food  plant  for  this  in- 
sect at  Marion,  S.  C,  May  29  to  June  14,  1909.  It  was  found  rarely 
on  toadflax  {Linaria  canadensis)  at  Marion,  S.  C,  from  May  26  to 
June  1,  1909,  and  abundantly  on  plantain  {Plantago  aristata)  at 
Marion,  S.  C,  June  3,  1909.  It  was  numerous  on  plantain  {Plantago 
majo7')  at  Sharpsburg,  Md.,  Juh^  9,  1907,  according  to  Mr.  Kelly,  and 
at  French  Creek,  W.  Ya.,  November  20,  1908,  as  reported  by  Mr.  F.  E. 
Brooks  in  a  letter  to  the  Bureau.  It  was  found  on  water  pepper 
{Polygonum  hydropiperoides) ,  May  22,  1909,  and  on  another  of  the 
knotweeds  {Polygonum  muhlenhergii)  ^  October  16,  1909,  at  Salis- 
bury, N.  C,  but  was  not  numerous  on  either  of  these  plants ;  it  was  re- 
ported also  as  abundant  on  purslane  {Portulaca  oleracea)  at  French 
Creek,  AY.  Ya.  It  was  abundant  on  poverty  weed  {Diodia  teres)  ^  at 
Marion,  S.  C,  May  31  to  June  14,  1909,  as  nearly  every  plant  of  this 
species  was  infested;  it  occurred  also  on  cocklebur  {Xanthium  cana- 
dense)  at  Marion,  S.  C,  June  1,  1909. 

This  insect  has  been  reported  and  described  from  Colorado  by 
Cowen  on  the  roots  of  mint  {Mentha  arvensis)  under  the  name  of 
Aphis  menthcB-radicis. 

All  the  known  wild  food  plants  infested  by  this  species  are  native 
to  the  eastern  United  States  except  the  following:  Amaranthus  retro- 
flexus^  A.  spinosuSy  and  A.  hyhridus^  which  have  been  naturalized 


104 


PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 


from  tropical  America ;  and  Chenopodimn  alhnm^  Capsella  hursa- 
pastorisy  Brassica  olemcea.   and   B.   nigra^  Polygonum  persicarla^ 

Rumex  crispus^  and  Anthemis  co- 
fvlcu  which  are  adventitious  from 
Europe  or  have  been  naturalized 
from  Europe.  They  are  all  annuals 
except  a  few  which  are  sometimes 
biennials. 

During  March  and  April,  1910,  in 
the  vicinity  of  San  Benito,  Tex.,  the 
writer  found  this  species  infesting 
the  roots  of  the  following  unculti- 
vated    plants:  Vervain      {Verhena 


canadensis),     common     nightshade 


Fig.  56.^Tho  corn  root-aphi 
rous  female  and  hind  tibia 
Forbes.) 


f         ^-^        e         ^?g«=/  {Solanum  nigrum)^  skullcap   {Scu- 

tellaria drummondii)  ^  Teucrimn 
laciniatum^  amaranth  {Aniaran- 
fhus  sp.).  Selenia  (?)  sp..  and  at 
Brownsville  on  the  roots  of  Iva 
xanthifolia  ( ?). 
Nothing  was  found  to  indicate  that  it  had  attacked  either  corn  or 

cotton,   although   further  investigations  will   be  required  to  either 

prove  or  disprove   its  occurrence   on 

these  or  other  cultivated  plants. 

INJURY   TO   CORN. 

Aphis  maidi-radicis  has  been  par- 
ticularly injurious  to  corn  in  Mary- 
land, Ohio,  Indiana,  and  Illinois,  and 
has  done  serious  injury  to  this  crop 
in  eastern  Pennsylvania,  New  Jersey, 
the  Virginias,  and  the  Carolinas.  In 
badly  infested  fields  the  crop  is  some- 
times almost  entirely  lost,  as  shown  in 
the  accompanying  illustration  (Plate 
V.  fig.  1),  from  a  photograph  by  Mr. 
W.  J.  Phillips,  of  a  field  in  Indiana. 

In  Illinois  its  seasonal  history,  ac- 
cording to  ^Ir.  J.  J.  Davis,"  is,  in  brief, 
as  follows:  The  eggs  may  be  found 
liatching  in  the  field  from  April  8  to 
Mav  22,  and  from  ten  to  twentv-two  venerations  mav  follow.  Sexual 
forms  (figs.  5G-58)  are  produced  in  the  latter  part  of  September  or  in 


Fig.  57. — The  corn  root-aphis 
less     male     and     antenna. 
Forbes. ) 


Wing- 
(From 


°Loc.  cit. 


Bui.  85,  Part  VI,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  V. 


Fig.  1.— Damage  to  a  Field  of  Corn  in  Indiana  in  1906  by  the  Corn  Root-Aphis 
(Aphis  maidi-radicis).    (Original.i 


Fig.  2.— Same  Field  a  Year  Later,  Showing  the   Effect  of  Applying   Barnyard 

Manure.    (Original.) 


CONTRIBUTIONS   ON    THE    CORN    ROOT-APHIS.  105 

October,  and  eggs  are  laid  in  October  and  November.  The  eggs  do 
not  hatch  until  the  following  spring.  Its  seasonal  history  in  other 
parts  of  the  country  does  not  appear  to  vary  materially  from  that  in 
Illinois. 

RELATION  OF  ANTS  TO  THE  ROOT- APHIS. 

The  life  of  the  corn  root-aphis  in  the  cornfields  is  so  dependent 
upon  that  of  the  cornfield  ant  {Lasius  niger  L.,  var.  americanus 
Emery) ,  and  vice  versa,  particularly  in  the  Middle  West,  that  they 
must  be  considered  together.  If  it  were  not  for  this  ant  the  great 
damage  that  is  done  to  corn  in  this  country  by  the  root-aphis  would 
be  impossible.  The  ant  is  distributed  everywhere  over  North  Amer- 
ica except  in  the  extreme  southern  and  southwestern  portions.  It  is 
found  in  cultivated  fields,  in  pastures,  in  forests,  and  along  roads. 
A  very  complete  account  of  the  life  history  of  this  ant  is  given  by 
Doctor  Forbes  in  the  Twenty-fifth  Eeport  of  the  State  Entomologist 
of  Illinois. 

The  ants  collect  the  eggs  of  the  aphis  in  the  fall  and  carry  them 
to  their  nests,  where  they  are  kept  during  the  winter.  By  bringing 
these  eggs  near  the  surface  or  carrying  them  deeper  down  into  their 
burrows  the  ants  are  able  to  control  the  hatching  of  these  eggs  until 
weeds  spring  up  upon  which  the  young  aphides  can  feed.  As  soon 
as  the  eggs  hatch  the  young  larvae  are  transferred  to  the  roots  of 
young  weeds  such  as  pigeon  grass,  smartweed,  and  ragweed.  "Wlien 
the  corn  begins  to  come  up  the  colonies  of  the  root-aphis  are  trans- 
ferred to  the  roots  of  corn.  The  root-aphis,  like  all  other  species  in 
this  family,  secretes  and  voids  a  sweet  liquid  called  honeydew,  upon 
which  the  ants  feed.  As  this  honeydew  constitutes  the  principal 
food  of  the  ants,  the  strength  of  each  individual  ant  colony  is  de- 
pendent upon  the  number  of  aphides  in  its  charge. 

Although  Lasius  niger  americanus  is  the  most  important  ant  that 
attends  Aphis  maidi-radicis  throughout  the  territory  known  to  be 
infested  by  the  root-aphis,  it  is  not  the  only  one  thus  involved.  Two 
other  species  that  are  important  in  this  connection  are  Lasius  flavus 
Fab.,  which  has  often  been  observed  attending  the  root-aphis  in 
Maryland,  and  Pheidole  vinelandica  Forel,  which  was  observed  by 
Mr.  J.  A.  Hyslop  attending  it  at  Nathalie,  Va.,  and  by  Mr.  G.  G. 
Ainslie,  at  Marion,  S.  C.  Among  the  ants  which  sometimes  attend 
this  species  are  Lasius  {Acanthomyops)  murphy i  Forel  found  asso- 
ciated with  this  species  at  Arlington,  Ya.,  by  Mr.  Paul  Hayhurst, 
and  the  following  species,  which  are  reported  by  Doctor  Forbes  °  as 
occasionally  attending  the  root-aphis  in  Illinois :  Formica  schaufussi 

o  Eighteenth  Report  of  the  State  Entomologist  of  Illinois.  Trans.  Dept.  Agr. 
111.  for  1893,  Springfield,  vol.  31,  p.  6G,  1894. 


106  PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 

Mayr,  Lasius  interject u.s  Mayr,  Myrmira  ficabnnocUs  Nyl.,  and  Sole- 
nopsis  deh'dls  Mayr. 

NATURAL   CHECKS. 

There  are  no  natural  checks  to  the  muhiplication  of  the  corn  root- 
aphis  and  its  attendant  ant  except  hard,  beating  rains  that  are  long 
continued.  The  thorough  soaking  of  the  ground  by  such  rains 
drowns  out  many  of  the  aphides,  and  also  the  young  of  the  ants. 

PREVENTIVE   MEASURES. 

It  happens  that  over  the  entire  territory  infested  by  the  corn  root- 
aphis  the  best  cultural  methods  for  the  growing  of  corn  independent 
of  insect  injury  are  just  the  methods  that  reduce  the  numbers  of  the 
corn  root-aphis  and  its  attendant  ant.  These  methods  are  crop 
rotation,  maintenance  of  soil  fertility,  and  early  plowing,  followed 
by  frequent  cultivations. 

CROP    ROTATION. 

The  system  of  rotation  that  gives  the  shortest  time  in  corn  is  the 
best.  In  the  cotton  belt  the  injury  from  the  root-aphis  will  be  less 
if  cotton  and  corn  are  not  allowed  to  follow  each  other  in  rotation. 
Outside  the  corn  belt  it  makes  no  difference  what  the  rotation  is  from 
the  standpoint  of  root-aphis  injury,  because  no  other  field  crop  is 
injured  by  this  insect.  Allien  an  old  cornfield  is  sown  to  some  rota- 
tion crop,  such  as  one  of  the  small  grains,  the  ants  are  unable  to 
find  food  for  the  aphis  except  on  the  roots  of  weeds,  which  are  soon 
killed  out  by  the  attacks  of  the  aphis,  or  are  smothered  by  the  grain. 
Large  numbers  of  the  aphis  will  then  acquire  wings  and  leave  the 
field.  There  is  some  evidence  that  others  are  eaten  b}^  the  ants,  but, 
one  way  or  the  other,  the  field  is  freed  of  them. 

MAINTENANCE    OF    SOIL    FERTILITY. 

The  maintenance  of  soil  fertility  by  the  direct  application  of  ferti- 
lizers does  not  lessen  the  numbers  of  the  aphis,  but  by  furnishing  the 
corn  23lant  with  sufficient  food  it  enables  it  to  make  a  strong  growth 
and  mature  a  crop  in  spite  of  the  aphis.  This  benefit  is  shown  in 
the  illustrations  (Plate  Y).  from  photographs  taken  by  Mr.  W.  J. 
Phillips  at  Richmond.  Ind. 

EARLY    PLOAVING,    FOLLOAVED    BY    FREQUENT    CULTIVATIONS. 

In  order  to  reduce  the  numbers  of  the  root-aphis  old  cornfields 
in  the  Xorthern  States  should  be  plowed  in  the  fall  or  early  spring, 
and  then  the  ground  should  be  stirred  several  times  before  planting, 
with  a  corn  cultivator  or  disk  harrow.  The  burrows  of  the  ants 
infrequently  go  deeper  into  the  ground  than  6  inches,  so  that  if  the 
ground  is  turned  over  and  thoroughly  stirred  their  nests  are  broken 


CONTRIBUTIONS    ON    THE    CORN    ROOT-APHIS.  107 

up  and  the  contents  so  scattered  that  the  ants  are  able  to  recover  only 
a  feAv  of  their  own  eggs  and  larvae,  and  fewer  yet  of  the  aphis  eggs. 
This  method  also  prevents  the  weeds  from  getting  a  start,  so  that 
there  is  no  food  for  the  young  larvae  which  hatch  from  those  eggs 
Avhich  the  ants  are  able  to  preserve.  This  is  a  good  treatment  for 
land  that  is  to  be  planted  to  corn  throughout  the  section  of  country 
where  the  root-aphis  is  found,  but  more  especially  in  tile  northern 
part  of  the  infested  territory. 

In  the  more  southern  part  of  the  range  of  this  insect  winter  plow- 
ing may  be  practiced  with  good  results  wherever  the  land  is  suffi- 
ciently level  so  that  it  Avill  not  wash  badl3\  Winter  plowing  breaks 
up  the  ants'  nests  and  scatters  the  contents  of  these  nests  at  a  time 
when  the  ants  are  least  able,  because  of  the  cold  wet  weather  and 
shortness  of  the  food  supply,  to  recover  from  the  injury. 

One  example  of  the  effects  of  winter  plowing  that  came  under  the 
observation  of  the  Bureau  of  Entomology  was  as  follows :  Mr.  John 
BoAvie,  at  Annapolis  Junction,  Md.,  plowed  the  major  portion  of  a 
60-acre  field  in  the  winter  of  1905-G,  leaving  unplowed  a  small  strip 
in  the  middle,  which  he  finished  in  the  spring.  Prof.  F.  M.  Webster 
visited  this  field  July  28,  1906,  and  found  that  owing  to  injuries  by 
the  root-aphis  the  spring-plowed  portion  of  the  field  would  almost  fail 
to  produce  a  crop,  while  the  winter-plowed  portion  gave  promise  of 
an  unusual  yield.  On  the  spring-plowed  area  much  of  the  corn  was 
missing,  while  many  of  the  surviving  stalks  were  dwarfed.  By  these 
signs  it  was  easy  to  determine  at  a  glance  the  dividing  line  between 
the  two  areas.  On  September  22,  1906,  just  after  the  corn  was  cut 
and  shocked,  this  field  was  visited  by  Mr.  C.  N.  Ainslie,  and  he,  too, 
was  able  clearly  to  separate  the  two  areas,  being  guided  only  by  the 
appearance  of  the  stubble. 

In  the  southern  part  of  its  range  the  corn  root-aphis  is  able  to 
spend  the  entire  summer  on  its  wild  food  plants,  and  these  wild 
plants  are  especially  infested  in  the  late  summer  and  early  fall.  If, 
then,  these  weeds  are  destroyed  by  thorough  cultivation,  the  root- 
aphis  is  encouraged  to  leave  the  fields.  In  the  fall  eggs  are  laid  on 
the  roots  of  late  scrub  corn  which  was  not  harvested  and  on  the  roots 
of  weeds  such  as  Ambrosia  and  pigweed.  Fall  plowing  as  soon  as 
possible  after  the  crop  is  harvested  will  prevent  these  eggs  from  being 
laid  in  the  field.    The  land  may  then  be  put  into  some  cover  crop. 

REPELLENTS. 

The  method  of  combating  the  root-aphis  by  direct  application  of 
repellents  to  the  seeds  was  investigated  by  Doctor  Forbes  and  re- 
ported in  the  Twenty-fifth  Report  of  the  State  Entomologist  of 
Illinois.  Many  substances  were  experimented  with,  such  as  oil  of 
lemon,  oil  of  cloves,  kerosene,  and  carbolic  acid.     Of  these,  oil  of 


108  PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 

lemon  appears  to  be  most  promisin<):.  A  solution  of  the  oil  in  alco- 
hol— 1  part  of  the  oil  to  9  parts  of  ordinary  connnercial  alcohol — is 
used.  About  3  ounces  of  this  mixture  is  used  to  a  gallon  of  corn.  It 
should  be  stirred  thoroughly  till  all  the  seed  is  moistened.  This 
treatment  costs  only  10  cents  an  acre  for  the  materials,  and  appears 
to  be  very  effective. 

INJURY  TO  COTTON. 

A  form  of  Aphis  inaidi-radicis  was  very  injurious  to  young  cotton 
on  the  light  sandy  soil  of  the  eastern  parts  of  North  Carolina  and 
South  Carolina  throughout  the  seasons  from  1907  to  1909.  During 
this  time  it  was  the  most  injurious  enemy  of  cotton  in  that  region. 
In  this  form,  which  is  apparently  the  same  as  that  found  on  corn  at 
Duncan,  Okla.,  by  Mr.  T.  D.  Urbahns,  of  this  Bureau,  the  spots  on 
the  back  of  the  apterous  vivipara  are  larger  and  darker  than  they 
are  on  the  typical  Aphis  maidi-radicis  as  found  on  corn  roots  in 
Illinois.  The  third  antennal  segment  has  two  or  three  circular  sen- 
soria  which  are  not  present  in  the  Illinois  variety.  Although  this 
insect  was  first  brought  to  the  attention  of  entomologists  as  a  cotton 
pest  in  1907,  some  of  the  cotton  planters  in  North  Carolina  have 
known  of  it  for  uj^ward  of  twenty  years. 

It  attacks  cotton  just  as  soon  as  the  young  plants  appear  above 
ground  and  is  usualh'  first  noticed  Avhen  the  plants  are  about  2  inches 
high.  The  cotton  plants  in  certain  areas  will  turn  red  and  die, 
shriveling  up  so  that  they  can  be  seen  with  difficulty.  In  one  field, 
examined  May  28,  1909,  at  Marion,  S.  C,  by  Mr.  G.  G.  Ainslie,  fully 
90  per  cent  of  the  cotton  was  infested.  As  a  rule  most  of  the  aphides 
observed  were  in  a  cluster  on  the  main  stem  just  below  the  surface 
of  the  ground,  but  a  few  could  be  found  an3^where  on  the  roots,  even 
to  the  tips  of  the  longest  rootlets.  Mr.  Ainslie  found  as  many  as 
200  insects,  in  all  stages,  on  one  plant. 

As  far  as  the  study  of  this  insect  has  gone  it  appears  that  the 
root-aphis  infests  cotton  only  while  the  plants  are  young  and  tender, 
and  leaves  as  soon  as  the  roots  begin  to  get  hard  and  woodj^ ;  or  they 
remain  only  on  the  fibrous  rootlets  deep  down  in  the  soil  where  they 
are  unable  to  do  much  damage.  They  leave  the  plants  as  winged 
migrants  or  are  transferred  by  the  ants  to  some  of  the  numerous 
wild  food  plants  of  this  species. 

The  ravages  of  this  insect  in  the  cotton  fields  can  be  largely  pre- 
vented by  proper  rotation  and  better  cultivation.  Most  of  the 
planters  reported  that  the  insect  was  less  injurious  where  cotton  was 
grown  after  cotton.  This  is  because  the  cotton  fields  are  usually  Avell 
cultivated,  so  that  when  the  root-aphides  leave  the  cotton  plants  they 
leave  the  cotton  fields,  and  their  eggs  are  not  left  in  the  fields  in  the 
fall. 


CONTRIBUTIONS   ON    THE    CORN    ROOT-APHIS.  109 

Many  of  the  planters  report  that  cotton  is  more  seriously  injured 
when  it  is  planted  after  corn.  This  is  because  the  root-aphis  can  feed 
on  the  roots  of  corn  all  summer  and  also  because  the  cornfields  are 
not  kept  clear  of  the  wild  food  plants  of  this  insect.  For  this  reason 
the  aphides  can  find  an  abundant  food  suppl}^  in  the  cornfields  all 
summer.  In  cornfields  as  far  south  as  Salisbury,  N.  C,  the  eggs  of 
this  aphis  are  laid  on  the  roots  of  late  replanted  or  scrub  corn  which 
was  left  uncut,  or  more  often,  perhaps,  on  the  roots  of  its  wild  food 
plants.  These  eggs  are  then  taken  into  the  burrows  of  the  ants  and 
cared  for  by  them  during  the  winter.  When  these  eggs  hatch  in  the 
spring,  the  young  larva^  are  placed  b}^  the  ants  on  the  roots  of  cotton 
or  corn,  if  these  crops  are  up;  if  not,  they  are  placed  on  weed  roots 
and  live  there  for  a  Avhile,  and  most  of  them  are  transferred  to  the 
roots  of  corn  and  cotton  as  soon  as  these  plants  become  available. 

If  corn  is  to  be  folloAved  b}^  cotton,  it  will  be  best  to  plow  the  land 
as  early  as  possible  in  the  fall  and  to  sow  to  a  cover  crop  later.  This 
will  prevent  the  eggs  of  the  root-aphis  from  being  laid  in  the  field, 
while  the  plowing  and  cultivation  will  break  up  the  nests  of  the  ants 
and  prevent  them  from  caring  for  the  eggs  that  are  laid.  The 
borders  of  the  field  should  be  kept  as  clear  of  weeds  as  possible. 

INJURY   TO   ASTERS. 

The  first  record  we  have  found  regarding  the  injury  of  a  root- 
aphis  to  the  Chinese  or  German  aster  is  in  an  article  on  ''  The  culture 
of  the  aster,"  by  Edward  S.  Rand,'^  in  which  he  says : 

The  earth  should  not  be  sandy,  as  in  such  soil  they  are  very  subject  to  the 
attacks  of  a  root-aphis,  which  always  proves  fatal  to  the  plant. 

And  again: 

For  the  root-aphis  which  troubles  the  plant  in  sandy  soils  we  know  of  no 
remedy  but  to  dig  up  the  affected  plant  and  destroy  the  insect. 

From  this  it  appears  that  the  root-aphis  was  well  known  as  a 
serious  enemy  of  the  aster  in  New  England  as  early  as  1858,  or  only 
about  thirteen  years  after  the  China  aster  became  numerous  there. 
A  later  record  is  found  in  the  Practical  Farmer  for  1875,  an  extract  of 
w^hich  is  given  in  the  Horticulturist  and  Journal  of  Rural  Art  and 
Taste,^  where  mention  is  made  of  the  "  dust}^  louse  "  Avhich  "  is  found 
at  the  roots  of  German  asters  in  hot,  dry  weather."  Watering  the 
asters  heavil}^  is  mentioned  as  a  remedy. 

The  first  record  in  the  files  of  the  Bureau  of  Entomology  in  regard 
to  this  pest  on  asters  is  an  inquiry  from  Washington,  D.  C,  in  July, 
1899.     Since  then  inquiries  have  come  from  the  following  States: 

«  Trans.  Mass.  Hort.  Soc.  f.  1858,  pp.  26,  27. 

^Horticulturist  and  Journal  of  Rural  Art  and  Taste,  vol.  30,  p.  366,  1875. 


110  PAPERS  OX  CEREAL  AND  FORAGE  INSECTS. 

Massachusetts,  Connecticut.  Rhode  Island.  New  York.  New  Jersey. 
Dehiware.  Maryhmd.  West  Virginia.  Ohio,  and  Illinois. 

Mr.  J.  A.  Kreutzberg,  writing  from  Chicago,  111.,  September  9, 
1908,  says: 

From  500  to  1,000  plants  grown  from  seed  early  every  year  in  the  hotbed, 
and  in  due  time  transplanted  in  the  open  ground,  rarely  more  than  one-third 
survive  and  pull  through  to  full  growth  and  beauty.  The  trouble  appears  to 
be  a  small  green  louse  which  looks  like  the  aphis  which  infests  the  rose  bushes, 
lodging  in  the  roots,  forming  large  colonies  in  them,  and  working  their  way  up 
in  the  plants  to  the  surface  of  the  ground.  Some  of  the  plants  are  blighted  as 
soon  as  they  are  set  in  the  open  ground,  some  later,  and  some  when  the  plants 
are  in  full  bloom.  The  moment  that  the  plants  are  attacked  by  these  parasites 
they  show  it  by  turning  yellow  and  wilting  down  to  the  ground. 

In  a  later  letter,  September  15.  1908.  he  says: 

I  this  morning  pulled  up  three  aster  plants  which  were  in  full  bloom,  yet 
showed  the  taint  of  the  ravages  of  the  aphis,  which  apparently  did  not  attack 
the  plant  until  quite  recently.  In  looking  over  my  aster  field  this  morning 
I  find  that  nearly  every  plant  is  affected,  which  was  conclusive  proof  to  me  that 
these  little  pests  begin  their  attack  during  all  stages  of  growth  of  the  plants. 
Some  are  attacked  immediately  after  transplanting  to  the  open  ground,  others 
a  little  later  on,  and  some  that  seem  to  have  strength  enough  to  pull  through 
and  are  in  bloom  are  attacked  after  the  bushes  are  loaded  with  flowers.  These 
three  plants  that  I  pulled  today  were  loaded  with  the  insects,  but  of  a  different 
color  than  I  have  found  them  heretofore,  but  apparently  the  same  genus. 

The  other  reports  are  much  the  same.  The  aphides  apparently  at- 
tack the  asters  as  soon  as  the}^  are  set  out  in  the  open  and  feed  on 
them  till  the  sexual  forms  appear  and  the  eggs  are  laid  in  the  fall. 
The  correspondents  often  report  that  the  aphides  are  attended  by 
ants,  but  onh'  one  species  has  been  taken  and  identified.  Lasifif<  alie- 
nvs  Forst  was  sent  to  the  Bureau  by  Mr.  C.  R.  Cranston  from  Provi- 
dence, R.  I.,  with  the  following  information : 

Just  as  the  [aster]  buds  begin  to  form,  the  leaves  all  turn  yellow  and  the 
plant  never  blooms.  On  pulling  some  up  I  found  that  ants  had  taken  green 
plant  lice  under  ground  to  suck  the  sap  from  the  roots. 

It  should  be  easy  to  keep  the  asters  free  from  this  pest  if  the  fol- 
lowing precautions  are  taken :  Choose  for  the  aster  bed  ground  that 
has  not  grown  asters  or  corn  for  the  past  year.  Free  this  ground 
from  the  wild  food  plants  of  this  species  some  time  during  August. 
Then,  if  there  is  no  crop  on  the  ground,  it  may  be  cultivated,  covered 
with  manure,  and  left  till  next  spring.  The  only  way  for  the  aphis 
to  reach  the  plants  on  this  ground  would  be  for  the  winged  migrants 
to  fly  to  the  plants  and  then  be  captured  and  taken  to  the  roots  by 
ants.  It  is  extremely  improbable  that  those  reaching  the  plants  in 
this  way  could  increase  in  numbers  fast  enough  to  do  serious  injury. 
In  fact,  if  the  asters  are  planted  in  ground  which  has  not  grown 
asters  or  corn  the  past  year,  and  which  is  not  located  near  a  field  of 


CONTRIBUTIONS   ON    THE    CORN    ROOT-APHIS.  Ill 

corn  or  an  infested  aster  bed,  they  Avill  not  be  troubled  with  this  pest, 
provided  the  wild  food  plants  of  the  pest  Avere  removed  from  the 
vicinity  of  the  bed  as  mentioned  above. 

OTHER  CULTIVATED  FOOD  PLANTS. 

A  root-aphis  Avas  reported,  in  October,  1908,  by  the  M.  CraAvford 
Company,  of  Cuyahoga  Falls,  Ohio,  to  be  injuring  straAvberry  plants 
in  a  field  Avhich  had  been  in  corn  the  jenr  before.  This  aphis  was 
identified  by  Mr.  Theo.  Pergande  as  Aphis  inaidi-radicis. 

Mr.  C.  H.  Popenoe,  of  this  Bureau,  collected  it  from  the  roots  of 
cabbage  at  Doncaster,  Md.,  July  24,  1907.  These  specimens  A^ere 
also  identified  by  Mr.  Pergande  as  Aphis  maid i-rad ids. 

These  aphides  were  found  to  be  injurious  to  pumpkin  and  Avater- 
melon  at  French  Creek,  W.  Va.,  in  July,  1908,  as  reported  in  a  letter 
from  Mr.  F.  E.  Brooks: 

I  haA'e  found  the  aphis  on  roots  of  watermelon  and  pumpkin  growing  wliere 
an  old  sod  of  orchard  grass  was  plowed  down  last  spring.  The  cucurbits  grew 
about  100  yards  from  a  cornfield  that  was  infested  last  season. 

AMiat  is  supposed  to  haA^e  been  Aphis  maidi-radicis  was  reported 
from  DoA^er,  Del.,  to  be  injuring  French  artichoke.  Mr.  Theophile 
Berneau,  of  DoA^er,  in  a  letter  to  the  Bureau  of  Entomology,  August 
25,  1908,  says: 

I^am  cultivating  French  artichoke,  Cynara  scolymus,  and  huve  some  trouble 
with  minute  insects  which  settle  on  the  roots  and  suck  the  sap,  to  the  great 
detriment  of  the  plant. 

Mr.  Berneau  reported  that  these  insects  Avere  accompanied  by  a 
great  number  of  ants. 

This  species  Avas  reported  as  injurious  to  dahlia  at  LongmeadoAv, 
Mass.,  and  at  Springfield,  Mass.,  in  1900.  In  a  letter  from  Spring- 
field dated  June  4.  1906,  Mrs.  T.  G.  Forster  says: 

I  haA'e  set  out  a  few  dahlia  bulbs  and  find  they  will  not  grow.  To-day  on 
unearthing  some  of  them  I  find  rhe  roots  and  also  the  sprouts — the  part  in- 
side the  ground — coA^ered  with  small  white  lice  w^iich  seem  to  eat  the  small 
new  roots  as  they  start  to  grow.     Have  had  some  trouble  with  them  before. 

DESCRIPTION  AND  SYNONYMY. 

There  is  some  question  as  to  whether,  in  our  study  of  this  insect, 
we  are  dealing  Avith  one  or  Avith  more  than  one  species.  There  is  a 
form  Avhich  feeds  on  the  fleabanes  (Erigeron)  and  on  wild  asters, 
described  by  Cyrus  Thomas  in  1879  as  Aphis  middletoni.  This  is 
probably  a  distinct  species,  although  further  study  may  show  that  it 
is  the  same  as  Aphis  maidi-radicis,  in  Avhich  case  both  forms  Avould 
be  known  as  Aphis  middletoni  Thos. 

Specimens  found  on  the  roots  of  corn,  in  Oklahoma,  by  Mr.  T.  D. 
Urbahns,  of  this  Bureau,  and  on  cotton,  u\  South  Carolina,  by  Mr.  G. 


112 


PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 


G.  Ainslie,  at  that  time  a  special  field  agent  of  this  Bureau,  are  about 
the  size  of  the  typical  Aphh  maidi-nulicis  but  they  have  circular 
sensoria — usually  about  three  on  the  third  segment  of  the  antenna — 
and  have  larger  and  darker  markings  on  the  thorax  and  abdomen 
than  has  the  typical  Aphis  inaidi-radicls.  This  form  is  without  much 
question  only  a  variety  of  the  true  Aphis  maidi-radicis.  It  seems 
best  at  the  present  time  to  recognize  two  species,  viz.  Aphis  middJe- 
toni  Thos.,  feeding  on  plants  of  the  genera  Aster  and  Erigeron,  and 
Aphis  maidi-radicis  Forbes,  which  feeds  on  corn,  cotton,  and  many 
wild  plants. 


Fio.  58. — The  corn  root-aphis  :   Winged  male,  greatly  enlarged,  and  antenna,  highly  magni- 
fied.     (Original.* 

Mr.  J.  H.  Cowen  describes  an  aphis  under  the  name  of  Aphis 
menthc^-radicis  Avhich  was  taken  on  Mentha  canadensis  at  Hotchkiss, 
Colo.,  Juh'  14.«  This  is  the  same  as  the  form  on  the  roots  of  corn,  and 
must  therefore  be  considered  a  synonym  of  Aphis  maidi-radicis.  In 
a  recent  letter  Prof.  C.  P.  Gillette,  entomologist  of  the  experiment 
station,  says: 

I  have  coDipared  the  type  specimens  with  the  slide  (Aphis  maidi-radicifi) 
you  sent,  and  am  a  little  in  doubt  as  to  whether  there  is  sufficient  difference  to 
consider  the  lice  from  the  mint  as  a  different  species.  I  hardly  think  they  are. 
It  also  seems  that  Mr.  Cowen's  annoracea  is  also  in  all  probability  maidi- 
radicis,  but  before  finally  deciding  this  matter  I  should  like  to  compare  the 

"  Description  published  in  "A  Preliminary  List  of  the  Hemiptera  of  Colorado." 
By  C.  P.  Gillette  and  Carl  F.  Baker.     Bui.  31,  Colo.  Agr.  Exp.  Sta.,  p.  121,  1895. 


CONTRIBUTIONS   ON    THE    CORN    ROOT-APHIS.  113 

living  lice  from  the  different  plants.     Armoracea  we  have  found  very  abundant 
here  on  horse-radish. 

As  very  complete  descriptions  of  the  different  forms  of  Aphis 
mddi-radicis  have  been  published,  no  descriptions  are  given  in  this 
paper  except  that  of  the  winged  male,  which  has  not  been  before  ob- 
served or  described.  Two  of  these  males  appeared  in  the  vials  in 
Avhich  Aphis  7)icddi-radicis  from  the  roots  of  Ambrosia  artemisii folia 
were  being  reared  on  corn,  and  one  in  the  vial  of  Aphis  from  Lep- 
tochloa  -pliformis.  Two  of  these  Avere  used  in  experiments ;  the  other 
was  preserved  and  is  described  below. 

Winged  S  (fig.  58). — Head,  thorax,  eyes,  and  appendages  black.  Abdomen 
green,  with  dark  transverse  bars  on  the  dorsal  side  of  the  5th,  6th,  and  7th 
somites.  The  beak  reaches  the  metathorax.  The  antennae  reach  the  caudal 
end  of  the  second  abdominal  somite.  The  circular  sensoria  are  arranged  on 
the  antennae  as  follows :  24  on  the  third,  12  on  the  fourth,  7  on  the  fifth,  4  on 
the  sixth.  Length  of  body,  1.50  mm. ;  length  of  wing,  1.75  mm. ;  length  of  cor- 
nicle, 0.10  mm.     (Measurements  made  from  specimen  mounted  in  balsam.) 

In  1856  Doctor  P^itch  described  the  corn  leaf-aphis  {Aphis  maidis), 
and  up  to  1891,  when  it  was  described  by  Doctor  Forbes,  what  is 
now  known  as  Aphis  maidi-radicis  was  supposed  to  be  only  a  root 
form  of  that  found  on  the  leaves.  No  one,  however,  has  been  able 
to  trace  a  sexual  relationship  betAveen  the  tAvo.  Although  the  sexual 
forms  of  A.  maidis  have  never  been  observed,  it  does  not  seem 
possible  that  such  a  relationship  as  was  preA'iously  supposed  can 
really  exist.  Besides,  while,  as  shown  by  map  on  page  114,  Aphis 
maidi-radicis  is  confined  to  the  country  east  of  the  one  hundredth 
meridian.  Aphis  maidis  occurs  from  Maine  to  southern  California. 

THE  ERIGERON  ROOT- APHIS. 
(Aphiii  middleioni  Thos. ) 

The  species  Aphis  middletoni  Thos.  is  considered  here  because  it 
has  usually  been  identified  as  Aphis  maidi-radicis  in  publications;  and 
because  it  is  impossible  to  study  one  of  these  forms  on  various  food 
plants  over  a  wide  extent  of  country  without  studying  the  other. 

So  far  as  is  noAv  knoAvn  Aphis  middletoni  infests  normally  plants 
of  the  genera  Aster  and  Erigeron,  usually  in  A^ery  large  colonies  at 
the  croAvn  of  the  plant  just  below  the  surface  of  the  ground  or  on  the 
large  roots.  The  only  cultiA^ated  plants  it  has  been  known  to  attack 
are  Cosmos  hipinnatiis  and  the  China  or  German  asters  {Callistephus 
hortensis)^  and  possibly  also  dahlias  and  French  artichoke  {Gynara 
scolymiis). 

Aphis  middletoni  Avas  first  described  by  Cyrus  Thomas,  in  1879,  in 
the  Eighth  Report  of  the  State  Entomologist  of  Illinois.  Since  then 
it  has  been  referred  to  in  literature  only  in  food-plant  lists.     It  has 


114 


PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 


generally  been  confused  with  the  corn  root-aphis,  and  when  found  on 
any  other  plant  except  Erigeron  it  has  usually  been  identified  as 
Aphis  maidi-radicis.  It  is  much  smaller  than  the  latter  species  and 
is  usually  more  heavily  powdered  with  a  waxy  material.  Its  corni- 
cles are  about  one-half  the  length  of  those  of  the  corn  root-aphis. 
The  third  antennal  segment  in  the  apterous,  viviparous  female  has  a 
group  of  5  or  more  circular  sensoria,  and  there  is  also  a  group  of  cir- 
cular sensoria  on  the  fourth,  and  sometimes  also  on  the  fifth  segment. 
In  the  typical  Aphis  maidi-radicis  these  circular  sensoria  are  not 
present.  The  winged  vivipara  are  smaller  than  those  of  Aphis  maidi- 
radkls,  have  shorter  cornicles,  and  circular  sensoria   on  the  third, 


Fio.  5'.). — Map  showing  distribution  of  Aphis  viaidi-radicis  and  Aphis  midillctoni  in  tlie 
United  States.  From  tlie  records  of  the  Bureau  of  Entomology.  #  Localities  in  which 
Aphis  maidi-radicis  has  been  found  or  reported  on  the  roots  of  corn.  x  Localities  in 
which  Aphis  maidi-radicis  has  been  reported  injurious  to  asters.  P  Locality  where 
Aphis  maidi-radicis  was  found  on  uncultivated  plants  only.  O  Localities  in  which 
Aphis  middletoni  has  been  collected. 

fourth,  and  fifth  antennal  segments,  while  Aphis  maidi-radicis  has 
these  sensoria  only  on  the  third  segment.  The  same  differences  arc 
found  in  the  oviparous  females. 

This  species  appears  to  have  been  a  native  of  the  Gretit  Plains,  but 
is  now  distributed  widely  over  the  territory  east  of  the  Rocky  Moun- 
tains, as  is  shown  in  figure  59. 


UNCULTIVATED    FOOD   PLANTS. 


Aphis  middletoni  has  been  found  on  the  following  wild  food 
plants:  On  Erigeron  canadensis^  mostly  in  the  Northwest;  on 
Erigeron  ramosus^  in  the  Carolinas;  on  the  roots  of  Aster  subulatus. 
at  Salisbury,  N.  C.,  from  May  22  until  September  22,  1909,  and  on 


CONTRIBUTIONS   ON   THE   CORN   ROOT-APHIS.  115 

Aster  ericoides,  from  September  18  until  November  15,  1909.  Sexual 
forms  were  found  on  this  plant  at  Salisbury,  N.  C,  November  15, 
1909,  and  at  Rockmart,  Ga.,  November  23,  1909.  Cosmos  (Cosmos 
Mpinnatus),  which  had  escaped  from  cultivation  and  was  growing 
wild  along  the  roadside  at  Salisbury,  was  also  found  infested  by 
this  aphis  in  October,  and  on  November  5  sexual  forms  were  present 
on  the  roots  of  the  i3lant. 

CULTIVATED  FOOD  PLANTS. 

Specimens  of  an  aphis  which  attacked  the  roots  of  China  asters 
(Callistephiis  hortensis),  received  from  Dr.  E.  P.  Felt,  of  Albany, 
N.  Y.,  apparently  belong  to  this  species,  but  specimens  collected  from 
the  roots  of  cultivated  aster  at  Chicago  by  Mr.  J.  J.  Davis  are  with- 
out any  doubt  Aphis  maidi-radicis.  It  is  yet  an  open  question  to 
which  species  the  insect  which  has  been  attacking  cultivated  asters 
in  the  North  Atlantic  and  New  England  States  belongs.  The  species 
which  attacks  dahlias  and  French  artichokes  {Cynara  scolymus) 
belongs  to  one  of  these  two,  but  to  which  one  can  only  be  settled  by 
obtaining  more  material.  Cosmos  hipinnatus  was  found  infested 
by  Aphis  middletoni  October  6,  1909,  at  Salisbury,  N.  C.  The  writer 
has  found  no  record  in  the  American  or  foreign  literature  of  an 
aphis  infesting  the  roots  of  dahlia,  artichoke,  or  cosmos.  Cosmos 
hipinnatifs,  which  grows  wild  in  Mexico,  may  have  been  one  of  the 
original  food  plants  of  this  species. 

ATTENDANT    ANTS.. 

The  Erigeron  root-aphis  is  attended  by  a  larger  number  of  ant 
species  than  is  Aphis  maidi-radicis.  It  is  seldom  found  associated 
with  Lasiiis  nigerlj.  var.  americamis  Emery,  which  commonly  attends 
the  corn  root-aphis,  but  is  ordinarily  found  attended  by  a  medium- 
sized  black  ant,  Cremastog aster  lineolata  Say,  which  on  the  other 
hand  seldom  attends  the  corn  root-aphis. 

Lasius  niger  americamis  was  observed  associated  with  this  species 
by  Mr.  J.  A.  Hyslop  at  Nathalie,  Va.,  July  9,  1908,  and  by  the  writer 
at  Salisbury,  N.  C.,  on  Cosmos  hipinnatus  November  5,  1909,  and  on 
Aster  ericoides  November  15,  1909. 

Cremastog  aster  lineolata  was  observed  associated  with  this  root- 
aphis  by  the  writer  at  Salisbury,  N.  C. ;  by  Mr.  G.  G.  Ainslie  at 
Clemson  College,  S.  C,  and  by  Mr.  Paul  Hayhurst  at  Ponca  City, 
Okla.,  Newkirk,  Okla.,  and  Wellington,  Kans.  At  Winfield,  Kans., 
it  was  found  by  Mr.  Hayhurst  associated  with  the  varieties  of  this 
ant  knoAvn  as  opaca  and  clara.  This  ant  and  aphis  were  also  found 
associated  at  Wellington,  Kans.,  by  Mr.  E.  O.  G.  Kelly. 


116  PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 

The  following  ants  were  found  associated  with  this  species  on  the 
roots  of  Erigeiori  canadensis:  By  Mr.  Hayhurst — Phe'idole  sp.  at 
Arkansas  Cit}',  Kans.,  Solenopsis  geminata  Fab.  and  Dorymyrmex 
pyramicus  Roger  at  Kingfisher,  Okla.,  and  I r^idomyrmex  analis  Ern. 
at  Xewkirk,  Okla. ;  by  Mr.  Kelly — Solenopsis  rnolesta  Say,  Lasius 
iiiterjectus  Mayr,  Monoviorium  minutum  Mayr  var.  minimum  Buck- 
ley, and  Ponera  coarctata  Latr.  var.  pennsylvanica  Buckley,  at  Wel- 
lington, Kans.;  by  Mr.  G.  G.  Ainslie — Pheidole  vinelandica  Mayr  at 
Marion,  S.  C.  The  ant  Prenolepis  impairs  Say  was  found  by  the 
writer  associated  Avith  this  root-aphis  on  Aster  ericoides  at  Eock- 
mart,  Ga. 

LABORATORY    AND     FIELD     EXPERIMENTS. 

Many  laboratory  experiments  were  carried  on  by  the  writer  at 
Salisbury,  X.  C,  to  determine  the  adaptability  of  Aphis  middletoni 
to  other  food  plants.  Wingless  females  were  taken  from  the  roots  of 
Erigeron  ramosus  and  transferred  to  sprouting  corn  and  to  sprouting 
cotton  in  vials,  and  although  this  experiment  was  tried  several  times, 
using  several  females  each  time,  it  was  unsuccessful.  A  number  of 
experiments  were  tried,  using  the  females  from  the  roots  of  Aster 
suhidatus.  These  also  were  unsuccessful,  with  the  following  single 
exception :  Females  removed  from  the  roots  of  Aster  suhulatus  to 
s2:)routing  cotton,  August  30.  produced  young  which  succeeded  in 
supporting  themselves  on  the  cotton.  Several  generations  were  pro- 
duced, but  the  aphides  never  acquired  the  characters  of  Aphis  maidi- 
radicis.  Oviparous  females  were  produced  October  9  and  others  were 
produced  later,  the  experiment  being  closed  Xoveml>er  22. 

Mr.  Kelly  carried  on  similar  experiments  at  Wellington.  Kans..  in 
1008.  which  were  more  successful.  His  experiments,  in  brief,  are  as 
follows: 

Experiment  D. — A  stem-mother  was  removed  from  the  roots  of  a  young 
Erigeron  plant  May  9  and  placed  on  a  young  Erigeron  plant  in  a  vial.  The 
young  which  she  produced  were  placed  on  sprouting  corn  in  vials. 

PZxperiment  D\ — One  young  born  May  10(?)  became  adult  May  19  and  pro- 
duced 45  young  between  May  20  and  .June  7. 

Experiment  F\ — One  larva  removed  from  cage  D  May  12,  matured  May 
22(  ?),  and  produced  35  young  from  May  22  to  June  2. 

Experiment  F^. — One  larva  from  cage  F\  born  May  22,  matured  May  30,  and 
I)ro(luced  32  young  from  May  .30  to  June  7. 

Experiment  V^. — Larvae  removed  from  the  above  experiment  May  30  did  not 
mature  on  corn. 

Mr.  G.  G.  Ainslie  carried  on  similar  experiments  in  1908  at  Clem- 
son  College,  S.  C.     The  most  successful  experiment  was  as  follows : 

A  few  aphides  from  the  roots  of  Erigeron  canadensis  were  placed 
on  sprouting  corn  in  a  vial,  October  30;  by  November  9  four  young 


CONTRIBUTIONS    ON    THE    CORN    ROOT-APHIS.  Il7 

had  been  produced  and  on  November  '20  one  wingless  viviparous 
female  remained  alive.    The  experiment  was  closed  November  20. 

These  experiments  show  that  the  Erigeron  aphis  can  be  transferred 
to  corn  or  cotton  roots  and  will  live  on  these  plants.  It  seems  to  take 
to  these  plants  more  readily  early  in  the  spring  or  late  in  the  summer, 
when  a  migration  from  a  Avild  food  plant  is  about  to  take  place.  The 
fact  that,  when  grown  on  corn,  this  aphis  still  retains  its  distinctive 
characters,  instead  of  acquiring  the  characters  of  Aphis  maidi-radicis^ 
goes  to  show  that  these  two  are  distinct  species. 

Mr.  Hyslop  and  Mr.  Kelly  carried  on  experiments  of  a  different 
nature  for  the  purpose  of  determining  these  points. 

Mr.  J.  A.  Hyslop,  on  July  29,  1908,  found  specimens  of  Erigeron 
canadensis  in  the  grounds  of  the  U.  S.  Department  of  Agri- 
culture at  Washington,  D.  C.,  badly  infested  with  this  aphis.  Near 
these  plants  he  planted  corn,  watermelon,  and  cucumber  seeds.  On 
September  23  he  pulled  all  of  these  plants.  The  Erigeron  plants 
were  infested,  but  no  aphides  were  found  on  the  other  plants,  even 
though  the  roots  intermingled  in  many  instances. 

On  August  11  Messrs.  Kelly  and  Urbahn«,  at  Wellington,  Kans., 
planted  corn,  squash,  cucumber,  and  watermelon  near  an  infested 
Erigeron  plant.  These  plants  w^ere  watched  till  October  12,  during 
which  time  the  aphides  continued  on  the  Erigeron,  but  were  found 
at  no  time  on  the  other  plants. 

Mr.  Kelly,  at  Wellington,  Kans.,  on  August  26,  1908,  planted  corn, 
w^atermelon,  cucumber,  squash,  and  pumpkin  seeds  near  infested 
plants  of  Erigeron  canadensis.  He  examined  these  plants,  Septem- 
ber 29,  but  found  aphides  only  on  the  Erigeron,  although  the  roots  of 
the  plants  often  intermingled. 

These  experiments  show  that  under  natural  conditions  in  the  field 
this  aphis  wdll  not  change  from  the  Erigeron  to  the  corn.  What  it 
would  do  if  forced  to  leave  the  Erigeron  is  uncertain,  but  we  have 
no  evidence  thus  far  that  it  can  live  for  any  very  long  time  on  the 
roots  of  corn. 

While  making  a  trip  through  the  Northwest,  in  June,  1908,  for  the 
purpose  of  studying  the  insects  affecting  cereal  and  forage  crops,  Mr. 
Kelly  made  a  careful  study  of  Aphis  maidi-radicis  and  A.  mid- 
dletoni.  At  Hastings,  Kearney,  Columbus,  and  Fremont,  Nebr.,  and 
at  Missouri  Valley  and  Marshalltown,  Iowa,  Aphis  maidi-radicis 
was  common  on  the  roots  of  corn ;  but  although  Erigeron  canadensis 
was  plentiful,  the  roots  sometimes  intermingling  w^ith  the  roots  of 
corn,  there  were  no  aphides  on  the  roots  of  Erigeron.  At  Bismarck, 
N.  Dak.,  and  Norton  and  Phillipsburg,  Kans.,  the  Erigeron  plants 
were  common  and  had  aphides  on  their  roots,  but  there  were  no 
aphides  on  the  roots  of  corn. 


118  PAPERS  ON  CEREAL  AND  FORAGE  INSECTS. 

At  many  of  the  toAvns  A'isited  neither  species  was  found,  although 
their  food  phints  were  plentiful.  If  these  two  forms  were  con- 
sidered to  be  one  species  these  results  would  be  very  difficult  to 
explain. 

At  Salisbury,  N.  C.,  a  colony  of  these  aphides  on  Aster  suhulatus 
was  found  parasitized  by  a  species  of  the  hymenopterous  genus 
Lysiphlebus.  This  colony  was  at  the  crown  of  the  plant  near  the 
surface  of  the  ground. 

o 


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